Condenser.



` A. PRUESSMAN.

. Patented June 8, 1909.

lfore it has been subjected to the preliminary UNITED STATES PATENT OFFICE.

ALBERT PRUESSMAN, OF CHICAGQVILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

CONDENSER.

i Specication 'of Letters Patent.

Patented .time 8, 1909.

Application led April 1, 1907. Serial No. 365,880.

My invention relates to an electric cone" denser and the process of making the same. Its object is to provide a condenser` which 1 shall be very compact, cheap to manufaci ture and in which the breakdown volt-age i and insulation resistance are extremely high, l

small size per unit capacity.

In carrying` out my invention, I first asy semble the strips of foiland dielectric lby -i rolling them together into the form of an elliptical or oval cylinder. This roll or cylinder is first baked, then placed in a mold, where it is pushed down to an approximately rectangular shape by pressure applied in the direction of its longest axis. Viihile held in the mold, it is boiled with melted paraflin wax orother insulating substance, and finally is placed in a press and subjected to pressure applied in the same direction as before. The mold prevents spreading at the sides, and the roll is thus pressed in the form of a prism. After the wax has been allowed to l cool and set, this prism isremoved from the mold and inclosed in the usual case to protect it and to prevent it from spreading apart.

My invention may be more readily understood by reference to the accompanying drawings, in which- Figure 1 is a perspective view showing the strips of tin foil and paper dielectric assembled in an elliptical or oval cylinder; Eig. 2 is a cross sect-ion of the roll in the mold and bepressure; Fig. 3 is a cross section of the roll in the press, showing its structure after it has been finally compressed; and Fig. 4 isa perspective view of the completed condenser as inclosed in its protecting case. v

Like parts are designated by similar char- Two sheets of tin-foil 1, and two layers of insulating material, each shown'as comprising three sheets of thin paper 2, are rolled into the form of an elliptical cylinder 3, as illustrated in Fig. 1. Saidroll is then placed in a rectangular mold 4, open at the top, the

i Fie. 3. i while at the same time the condenser is of diiiided by diagonals into four parts, the

layers' of the upper and lower parts are in it can be inserted in its case.

j wid th of said mold being approximately that of the shortest diameter of the roll.

A rectangular block 6 is placed above the roll 3, and pushed down by hand, so that pressure 1 is, through said block, exerted upon the roll 3 in the direction of its longest axis. After i the condenser has been boiled in paraflin, the i mold is placed in a press 5, andsubjected to a final pressure exertedin the same direction as in the irst'instance. As a result of such pressure, the roll is compressed into an api proximately squareshaped prism, the layers assuming approximately the shape shown in Thus if we considerthe prism to be straight lines, while those at the sides have a wave-like formation. The pressure in the press 5 is maintained until the wax or paraffin has hardened, whereupon the condenser is removed and iinally placed in a tightly fitting case 7, which is sealed in the usual manner.

I am aware of the fact that it has been proposed that sheets of paper and tin-foil be formed into a flat roll and then compressed into a still latter form. I am also aware of the fact that in order toV overcome the objections to said flat form of condenser and to get a compact condenser of approximately square cross section, it has been usual to fold such flat roll into an S-shape or U-shape, and then exert pressure upon the' same. The difiiculty with the latter form of condenser is that if a thick dielectric is used, as for example three sheets of paper, the folding becomes difficult and there is atendency of the parts to unfold or spread apart after pressure, thus defeating the very purpose in view. It has been found that there is a considerable loss due to the unfolding of the condenser before In the condenser of my invention, however, the condenser remains in its pressed condition, and there is no loss from this source.

With the folded type of condenser, in obtaining two mierofarad capacity in a given bulk, it has been found that the condenser withstands a maximum breakdown voltage of approximately only six hundred and fifty volts, ranging as low as three hundred volts.

As it is customary to test lcondensers at ve l hundred volts, all below tive hundred volts being rejected, it has resulted that a large proportion, approximately twenty per cent.

of such condensers, do not come up to the required standard. .In the condenser of my invention, it has been found by repeated tests that the range of breakdown is fromfive hundred and seventy five to twelve hundred and fifty volts, or, in other words, that all pass the required fivehundred volt test. This marked increase in eiiiciency is doubtless due largely to the increased thickness of the dielectric which the absence of folds permits me to employ.

I have found that, owing to the manner in which the pressure is applied in my invention, it is possible to compress a condenser having three sheets of insulating paper between the tin foilinto the same compass as a condenser having the same amount of tinfoil separated by two layers of paper and which is compressed in the manner heretofore employed. l

I-Iitherto it has been found necessary to employ a high and expensive grade of paper as a dielectric, for the reason that with only two sheets there is, unless such grade of paper be employed, extreme liability .of flaws coinciding and thus reducing the dielectric strength and insulation resistance. With my invention, it is possible to employ three or more sheets of paper, thus reducing the possibility of defective spots or flaws thus coinciding, and rendering it practicable to employ a lower grade of paper and still obtain the same or even a higher dielectric strength and insulation resistance. It is further obvious that, since the folding of the roll is dispensed with, there is less handling of the same in the process of manufacture. For the foregoing reasons, the practice of my invention results in a very compact and efficient condensei, manufactured comparatively cheap.

I claim:

1. The process of making condensers, which consists in rolling the strips of foil and insulating material in an elliptical cylinder, and subjecting such cylinder to pressure in a rectangular mold, said pressure being imparted in a manner to shorten the longer diameter of the cylinder, and to compress said cylinder into approximately a prism.\

2. The process of i making condensers which consists in assembling the strips of foil and insulatingmaterial in a thick cylindrical roll of elliptical cross section, treating the same with melted wax, and subjecting the same to pressure in a mold', While allowing the wax to cool and set, the pressure being applied in such-way as to shorten the diameter of the cylinder and to compress said cylinder into an approximately square prism.

3. The process' of making condensers which consists in assembling strips of plates and dielectrics into a thick cylindrical roll of elliptical cross section, placing said cylindrical roll in a rectangular mold, and applying pressure lin such a manner as to shorten the onger diameter of the roll and to compress said roll into a prism.

4. The process of making condensers which consists in assembling stri s of plates and dielectrics into a thick cylin rical roll of elliptical cross section, lacing said cylindrical roll in a rectangu ar mold having a Width ap roximately equal to the shorter axis of the el ipse, and applying pressure in such manner as to shorten the longer diameter of the roll and to compress said roll into a prism.

5. The process of y making condensers which consists in assembling strips of plates and dielectrics into a cylindrical roll, and a plying pressure upon four sides of the roll, viliile said roll is in the cylindrical form, 1n such manner as to compress the same into a prism of approximately square cross section.

6. An electric condenser in the form of a rectangular prism, consisting ofcontinuous alternate layers of plates and dielectrics,

compressed on its four sides in such formi that the diagonals of the rectangle divides the rectangular prism into four approximately triangular prisms, two of which have parallel straight layers, and the other. two parallel Wave-like layers.

In Witness whereof, I, hereunto subscribe my name this 28th day of March A. D. 1907.

ALBERT PRUESSMAN.

. WYitnesses: i

RALPH G. JoHANsEN, RALPH W. INGERsoLLi 

